<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<script>

//原型链 : 实例对象与原型之间的连接，叫做原型链

//原型链的最外层 : Object.prototype

function Aaa(){
	//this.num = 20;
}
//Aaa.prototype.num = 10;
Object.prototype.num = 30;

var a1 = new Aaa();
alert(a1.num);

</script>
</head>

<body>
</body>
</html>
